Celtic Thunder duo Neil Byrne and Ryan Kelly go acoustic (VIDEO)

Celtic Thunder has been thrilling audiences for the past six years. They’ve racked up a string of successful albums connected to big production tours.

The juggernaut sees no sign of slowing down, with a Celtic Thunder cruise, another record-breaking tour, Mythology, booked through June of 2014, and a Christmas CD on the way.

Say what you will about the glitzy production — it has done an enormous amount of good for Irish culture by shining a much-needed spotlight on great songwriters and producers like Paul Brady, Phil Coulter and Christy Moore. It has also launched the careers of some great Irish artists, including Glee star Damian McGinty and Paul Byrom.

Cast members Ryan Kelly from Moy, Co. Tyrone and Neil Byrne from Bray, Co. Wicklow began performing a live show together called “Acoustic by Candlelight” during the nights off from the Celtic Thunder tour, and that has now developed into an album titled Acoustically Irish.

“We wanted to give us our own signature. We wanted the listeners to have this organic feel to it,” Kelly explains.

“Celtic Thunder has a full orchestra; it is very lush. We wanted to have a more intimate setting. Fans that came out to see us said they wanted an album from the candlelight shows, so the decision to put out an album came from that.”

Fans of traditional Irish music will love their takes on songs like “On Raglan Road,” “Back Home in Derry,” “The Fields of Athenry,” “The Rose of Allendale” and “The Water Is Wide.”

The lads also offer a bluegrass reading of Hothouse Flowers’ “Don’t Go,” a coffee house-cozy rendition of Van Morrison’s “Brown Eyed Girl” and a heart-tugging run at Paddy Casey’s gorgeous “Saints and Sinners.”

The album is a welcome, organic departure from the glitzy Broadway feel of the Celtic Thunder franchise.

The fans seem to be eating it up, catapulting this heart-throbbing duo to the top position on Billboard’s World Album chart and the top spot on iTunes World Album downloads in the U.S., Canada and Australia.

They borrowed Celtic Thunder bandmates Nicole Hudson on violin and viola, Declan O’Donoghue on percussion and Barry Kerr on tin whistle to create a zesty Irish backdrop to their shimmering harmonies.

I spoke to the guys about this new venture and the future of Celtic Thunder. Here’s how it went:

How did you decide to work together?

Ryan: Neil and myself were often doing these PBS things on tour and the six of us were often split up. Neil and I did an East Coast PBS tour. We have common ground on what we like, and we thought, wouldn’t it be great to break off on our own. We wanted to bring it back to where we began — the smaller gigs in pubs.

You play characters in this Celtic Thunder showcase: Ryan plays the rogue, Neil the clean-cut lad. I would imagine being yourselves onstage is pretty liberating?

Neil: It’s great to be able to have both. The side interest in Acoustically Irish is great. As you said, we have these characters. Our true personalities come out more in these gigs. We get to choose what we wear, what we play and everything else. So, yes, that is liberating.

How did you pick the tunes?

Ryan: The likes of “Raglan Road” and “Fields of Athenry” are things we grew up singing. They are great stories. “Don’t Go” by Hothouse Flowers and “Saints and Sinners” from Paddy Casey reflect the more modern, eclectic tastes that Neil and I have.

Neil: We thought putting more of our favorite songs by these artists might be interesting. “Captured” is Brian Kennedy’s song. He should be a household name. It’s like we’re bringing a new song out because unfortunately people haven’t heard these songs before. We are hoping to fix that.

Have any of the artists given you feedback on what they thought of your rendition?

Ryan: A while ago we sent Brian Kennedy a demo of “Captured” and he really liked it. He put up a nice comment about it on Twitter. “No Man’s Land” was written by Art Bogle; he wrote “The Green Field of France” and “The Band Played Waltzing Matilda.” Just a great, unsung songwriter, and he was really supportive of us doing his songs.